Corona Daily 354: Trust Your Dog’s Nose

Did you visit Dubai recently? Unlikely.

Those who did were taken to a private room at the Dubai airport. A border official took a sample of sweat from the passenger’s armpit. In another room, a trained K-9 sniffer dog smelled it to decide whether the passenger was infected by coronavirus or not.

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Over the last few months, dogs have been intensively trained in the USA, UAE, Chile, Finland, Australia, Germany, Argentina, Brazil and Belgium. Most studies conclude dogs can sniff and detect the virus with over 95% accuracy. Chile trains Labradors and Golden Retrievers. Saudi Arabia Jack Terriers. UK has Labradors and Cocker Spaniels.

Scientists at the London School of Hygiene and Tropical Medicine are currently recruiting volunteers to help train dogs. Volunteers with mild symptoms need to give samples of breath and body, wearing a mask for three hours and nylon socks and t-shirt for 12 hours. The aim is to collect 325 positive and 675 negative samples to train dogs.  

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Since April, the University of Pennsylvania has trained eight Labradors and one Belgian Malinois. A dog is let into the room that contains a giant horizontal metal wheel. The wheel has metal cans, each containing urine samples from patients testing positive or negative. The Labrador sniffs each can, and stops at the container with a positive sample.

Olfactory disease detection is an evolving field. We know the simple mechanism of a breathalyzer for levels of alcohol. A dog’s nose has 300 million receptors compared to 5 million in a human. Dogs can be trained to smell drugs, explosives, some hidden cancers, diabetes, malaria and other infections.

Changes in our health alter the way we smell. Spouses of some patients with Parkinson’s have noted their partners smelling differently. Human bodies give off a cocktail of chemicals known as VOCs (volatile organic compounds) in sweat, saliva, urine, breath and sebum that change when cells grow. When infected by a virus, some cells die and the smell changes. Dogs don’t detect Covid, but they detect the cells dying because of the virus infection.

To systematically train a dog to detect the novel coronavirus, it takes 6-8 weeks if the dog is already trained to detect other scents. A new dog needs 3-6 months. How does the dog know the object of detection? Like in a circus, the dog is initially “bribed” for performance. When the Labrador or German shepherd smells a “positive” can, it is given a pet food - Kibble. At the “negative” can, nothing. Over the weeks, the Labrador realizes the trainer is interested in finding the “positives”. The dog is also interested, because it gets a kibble every time. After two months, it stops at a positive can, and looks at the trainer to indicate victory. By this time, bribing can stop.

In a single case, one Labrador made a mistake. It stopped at a “negative” can. When investigated, it was found that the patient had earlier tested positive, and the smell had lingered.

Like human beings, dogs also come with superior ability, inferior ability and laziness.  A dog can sniff 250 people per hour. This is hard work. (It’s a dog’s life). Not every dog manages this. The best ones are chosen for airports. After UAE, Saudi Arabia will employ them soon at its international airport.

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Dogs are accurate, but require long training and expensive maintenance. “Electronic noses” are now invented that successfully detect toxic gases and explosives. Scientists believe they are the future. Until then, airport authorities will continue to trust the noses of the Labradors.

Ravi